[PATCH v2 4/8] KVM: x86: nSVM: Set vmcb02.g_pat correctly for nested NPT

[Jim Mattson]

When nested NPT is enabled in vmcb12, copy the (cached and validated)
vmcb12 g_pat field to the guest PAT register. Under KVM, the guest PAT
register lives in the vmcb02 g_pat field.

When NPT is enabled, but nested NPT is disabled, copy L1's IA32_PAT MSR to
the vmcb02 g_pat field, since L2 shares the IA32_PAT MSR with L1,

When NPT is disabled, the vmcb02 g_pat field is ignored by hardware.

Fixes: 15038e147247 ("KVM: SVM: obey guest PAT")
Signed-off-by: Jim Mattson <jmatt...@google.com>
---
 arch/x86/kvm/svm/nested.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index e65291434be9..b0c0184e6e24 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -656,9 +656,6 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm 
*svm, struct vmcb *vmcb12
        struct vmcb *vmcb02 = svm->nested.vmcb02.ptr;
        struct kvm_vcpu *vcpu = &svm->vcpu;
 
-       nested_vmcb02_compute_g_pat(svm);
-       vmcb_mark_dirty(vmcb02, VMCB_NPT);
-
        /* Load the nested guest state */
        if (svm->nested.vmcb12_gpa != svm->nested.last_vmcb12_gpa) {
                new_vmcb12 = true;
@@ -666,6 +663,19 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm 
*svm, struct vmcb *vmcb12
                svm->nested.force_msr_bitmap_recalc = true;
        }
 
+       if (npt_enabled) {
+               if (nested_npt_enabled(svm)) {
+                       if (unlikely(new_vmcb12 ||
+                                    vmcb_is_dirty(vmcb12, VMCB_NPT))) {
+                               vmcb02->save.g_pat = svm->nested.save.g_pat;
+                               vmcb_mark_dirty(vmcb02, VMCB_NPT);
+                       }
+               } else {
+                       vmcb02->save.g_pat = vcpu->arch.pat;
+                       vmcb_mark_dirty(vmcb02, VMCB_NPT);
+               }
+       }
+
        if (unlikely(new_vmcb12 || vmcb_is_dirty(vmcb12, VMCB_SEG))) {
                vmcb02->save.es = vmcb12->save.es;
                vmcb02->save.cs = vmcb12->save.cs;
-- 
2.52.0.457.g6b5491de43-goog